In general, a power conversion device for an electric motor vehicle according to the related art is configured to collectively drive, in parallel, with one inverter circuit in the power conversion device, a plurality of induction motors directly connected to axles mounted on trucks of the electric motor vehicle.
Usually, in many examples, the power conversion device of this type is configured to collectively control, in parallel, with one inverter circuit, four induction motors that respectively drive four axles in total incorporated in trucks arranged at both ends of the electric motor vehicle.
Further, in a power conversion device for driving an electric motor vehicle that travels in an alternating-current section, a converter circuit for once converting alternating-current power received from an overhead wire into a direct current and supplying the direct current to an inverter circuit is added.
As a cooling system in the power conversion device for electric motor vehicle driving, for a reduction in the size and the weight of the device, a forced air cooling system for circulating the external air with a cooling fan to cool an inverter circuit and a converter circuit (both the circuits are hereinafter generally referred to as “power conversion circuit”) is the main stream (e.g., Patent Literature 1).